The present invention relates generally to thin film magnetic recording head fabrication processes, and more particularly to such processes which fabricate heads incorporating polyimide layers which encapsulate the coils thereof, and to processes which accurately control the formation of coil via, magnetic shunt via and apex taper therein.
The existing state of the art in fabricating thin film magnetic recording heads employs photoresist material as an encapsulant material surrounding the coil portion of the recording head. Use of such photoresist materials only permits processing temperatures on the order of 300 degrees Celsius. Consequently, amorphous yoke materials cannot optimally be employed in such recording heads, since post-deposition processes of such materials require processing temperatures between 350-400 degrees Celsius in order to properly tailor the magnetic properties of the recording head. The advantages of using amorphous yoke materials and processing at 350 degrees Celsius has been suggested by K. Yamada et al in an article entitled "A Thin Film Head for High Density Magnetic Recording using CoZr Amorphous Films," in Applied Physics, Volume 55, page 2235 (1984). The ability to process the encapsulated coils at such elevated temperatures is highly desirable, since it is generally necessary to tailor the magnetic properties of the films. The tailoring of the magnetic properties of such recording heads is discusses in articles by H. Sakakima entitled "Properties of Amorphous Alloy films Mainly Composed of Co-Nb2," in IEEE Transactions on Magnetics, Volume 19, page 31 (1983), and Y. Shimada in an article entitled "Amorphous Co-Metal films Produced by Sputtering," in Phys. Stat. Sol.(a), Volume 83, page 255 (1984).
The existing state of the art in fabricating thin film magnetic recording heads employs photoresist material as an encapsulant as is disclosed in U.S. Pat. No. 4,539,616, entitled "Thin Film Magnetic Head and Fabricating Method Thereof," issued to Yuito et al. An article by Shiiki et al entitled "Fabrication of Coils with High Aspect Ratios for Thin Film Magnetic Heads," in J. Vac. Sci. Technol. Volume A3, page 1996 (1985) presents substantially the same information as is contained in the above-cited patent. The motivation for incorporating polyimide as described in the above references, is to achieve high aspect ratio coils through a lift off process.
In addition, the formation of coil via, magnetic shunt via and apex angle taper of the recording head has utilized the deposition of several layers of photoresist deposited over the encapsulated coil. The layers of photoresist are photolithographically patterned and reflowed at elevated temperatures to generate the desired apex angle profile, vias and coil planarity. The reproducibility of this processing is critically dependent upon the control of resist properties and baking conditions. In addition, the coil planarity and the apex profile cannot be optimized independently, since both occur during the same reflow operation.